1. Field of the Invention
The present invention is related to the field of signal transmission. More specifically, the present invention is a method and apparatus for switching input terminals based on a device's capability.
2. Related Art
Use of digital interfaces is a trend in signal transmission, as a result of recent developments in digital signal processing technologies. Analog video and audio signals are digitized and coded, or compressed, before being transmitted. Various types of compression techniques, including DVI (Digital Video Interactive) and MPEG (Motion Picture Experts Group) compression, have been developed to achieve high-performance digital signal transmission. Standards developed for digital interfaces, such as IEEE1394, allow digital signals in various formats to be transmitted through a single digital interface. Such standards, however, do not regulate the formats in which the signal is coded, nor control the transmission path through which the signal is transmitted.
It is vital to ensure that a device that receives a digital signal in a particular format is capable of decoding it to recover an original signal from it. This requirement was relatively easy to satisfy when digital signals were coded and transmitted in a limited number of formats such as the DV (Digital Video) format. Development of digital signal processing technologies has led to different formats, and distinctive modes exist for some formats with regard to the transmission speed and bandwidth of the signal. Devices that receive and use transmitted signals are not necessarily provided with decoders corresponding to the various formats, due to economic reasons. One problem that has emerged is that an incoming signal is not always received in a usable format, and if this is the case, a device using the signal cannot decode the transmitted digital signal. A digital TV that can process digital signals exclusively in the format based on the MPEG Standard, for example, cannot process signals coded in the DV format or the DSS (Digital Satellite System) format.
In addition to the differences between the coding formats of digital signals, signals are not always transmitted in a digital format but also in an analog format, particularly in a transition period from analog to digital, while both formats are in use. In other words, analog signals can co-exist with digital signals.
Some transmitters and receivers, having both analog and digital interfaces, are designed to process digital signals as well as analog. In order to transmit an analog signal to such a device, the signal has to be transmitted through the analog interface. Otherwise the signal cannot be transmitted to the receiver. It is vital, therefore, to select an appropriate transmission path, i.e., the digital interface or the analog interface, depending upon the type of the signal, digital or analog.
For the foregoing reasons, there is a need for a method for switching input terminals based on a device's capability.